Oil burner



Dec. 29, 1936. E. o. BENJAMIN OIL BURNER Filed NOV. 7, 1933 INVENTOR (QM ATTORNEY Patented Dec. 29, 1936 UNITED STATES FATE7T OFFIQE 13 Claims.

My present invention relates more particularly to oil burners of the gun type, which is one of the very common types employed for oil burning furnaces. In this type of burner a barrel or conduit-projects laterally, usually horizontally, into the fire box. A centrifugal fan delivers a blast of air through this conduit and some form of jet is located within the conduit near the discharge end for discharging atomized liquid fuel, which mixes with the air blast.

My invention relates more particularly to means for mechanically atomizing, mixing and projecting the oil in novel relation to the air blast. For this purpose, I employ a rotary motor-projcctor unit of novel form, in which the same elements that atomize, mix and project, also function as motor elements which are propelled by the air blast. Preferably, the rotary motor-projector is arranged as a valve, which automatically opens and closes the oil supply passage, upon starting and stopping.

The above and other features of my invention will be more evident from the following description in connection with the accompanying drawing, in which Fig. l is a longitudinal section showing the air conduit, blower and air-driven rotor;

Fig. 2 is a longitudinal section on the line 2-2, Fig. 1, showing on a larger scale the air driven rotor and oil supply tube with which it is associated:

Fig. 3 is a section on the line 3-3, Fig. 2, showing said rotor in rear elevation; and

Fig. 4 is a face View of a modified form of the air driven rotor.

In the drawing, the centrifugal blower l delivers a blast of air through the horizontal conduit 2. The annular flange 3 is intended to abut against the wall of the furnace, the parts at the left of said flange projecting within the fire box.

Oil is supplied from a suitable source through supply pipe 4, communicating with the axially disposed pipe 5, the forward end of which may be supported by a spider as shown at 6.

On the forward end of pipe 5 is the motormixer-sprayer unit, which comprises the pipe I having an enlarged base 8, preferably provided with square or polygonal faces for engagement with a wrench or other tool for screwing it into pipe 5.

As shown more clearly in Fig. 2, the pipe 1 forms a support for the rotary motor-sprayer mechanism. The rotor consists of a cup-like windwhe'el, preferably made from thin rolled sheet steel or bronze. The convex outer surfaces of the (Cl. HES-77) cup, are presented rearwardly for impingement by the air blast. The central portion comprises fan-like blades bent to form a relatively flat cone portion 9, extending some distance from the flat central portion is, and then bent to form a peripheral conical rim 9a of much steeper pitch.

The flat central portion 10 is clamped between annular flanges H and l2, flange ll being carried by an outer tubular hub member l3, which is slightly smaller than the interior of tube 1, so as to afford clearance for flow of the oil; and flange l2, carried by an inner tubular hub member !4 which is screw-threaded into the interior of 13.

This windwheel unit is rotatably mounted in the tube 1 by means of a longitudinal member l5,

which is non-rotating and constitutes an axle for the rotating parts.

As shown in Fig. 2-, the axle l5, which may be a steel needle, is passed through I4, which is preferably of brass or bronze; then through a washer Iii, which is preferably of steel; and then through a conical member H, which is preferably of brass; and the projecting end If! is upset or flattened to prevent withdrawal. When these parts are assembled in the tube 1, a spring I9, seated in the rear enlargement 29, is compressed and a bent portion thereof 2! is hooked through an eye 22 at the rear end of axle 15, so the latter is under constant rearward tension.

As shown, the cylindrical interiors of the cone element I1 and hub screw element l4 fit the axle l5 somewhat loosely and the exterior of I3 is smaller than the interior of 1, so that said cone, hub and axle are all free for slight angular as well as vertical and longitudinal movement with respect to one another and with respect to the sta tionary tube 1. Consequently, the rearward spring tension which the flattened portion H! of axle Iii exerts on the conical piece ll, its transmitted with such freedom that the rear surface of the annular flange ll automatically tends to seat itself squarely on the forward end of .I, thereby closing the oil annulus.

The compression of the spring I9 is predetermined or adjusted to hold said flange ll. against the end of tube 1, with pressure strong enough to safely close the oil outlet against the normal pressure of the oil supplied through pipe 4; but much too weak to withstand the much higher air pressure that is exerted on the surfaces 9, 9w, when the air blast is impinging thereon. Consequently, the valve automatically opens when the blower applies the air pressure and is automatically shut off when the blower stops.

The member I! is long and tapered, as shown,

symmetrical and very light as well as symmet-- peripheral structure.

for the purpose of serving as a stream-lined filler to prevent formation of a partial vacuum, and reverse eddying of the flame when the air blast is rotating the windwheel at high speed.

When the air blast is on, the windwheel is forced away from the end of 'l, as shown in Fig. l, leaving an annulus for escape ofoil. When in this position, the rotor is perfectly centered because the rear surface outline of the rotor is a double cone, the flatter fan blade come as shown at 9 and the steeper rim-cone as shown at 9a. The rim cone 9a rotating closely adjacent the interior wall of the conduit is specially effective as a means automatically centering the rotating parts, when they are no longer positioned by c ontact of the rear face of I I with the end of tube 1.

When in operation, a further centering effect is afforded by the stream of oil flowing through the annulus between the hub l3 and the tube 1. The diameter of this annulus may vary in accordance with the size of the burner, and the viscosity of the oil, but a clearance within a range of 1/100 inch to 1/50 inch will ordinarily suit the conditions. It will be obvious that the film of viscous oil passing through this space is centrifugally whirled by the hub I3, thereby establishing a substantially uniform annular oil bearing capable of centering and sustaining the relatively light weight of the rotor.

, r In this connection, it may be noted that a centrifugal fan maintaining the air blast at a pressure ofsay inch to 1%.; inches (water head) will spin 'a wind-wheel of, say, 1 inch diameter at speeds as high as 3,000 or 4,000 R. P. M.

rically balanced and of sufl'icient structural strength to withstandthe stresses developed during practical operation of the device.

One practical Way is to take a sheet of thin fine sheet metal, say. steel, preferably rustless steel, and first cut it out as a circular disc. For the wheel shown in Fig. 3, this circular disc would have the radius and periphery indicated ;by the line M. This disc is then slitted radially, as indicated in dotted lines, up to the periphery of the flat central portion I!) (Fig. 2). The blades are then twisted to the proper pitch.

When so twisted, open spaces will appear between them as at b, Fig. 3. Preferably, in the same operation, the blades are bent to form the flat cone 9 for the body portion, and the steep cone Safor the peripheral portion. When the blades are thus bent from the original radius a-a, to the smaller radius of the completed article, the bent-up edges 9a substantially overlap one another. The bend at the junction between the body portion Sand the peripheral portion 9a instead of being on the lines of a regular polygon, is skewed so that the trailing edge of one portion 90. laps behind the leading edge of the adjacent portion 901.. These overlapping portions are anchored in contact so as to constitute a complete In the form shown in Figs. 2 and 3, the overlapping edges are secured by bending over a tag and punching the overlap as at 9d. A simpler and preferable way is that shown in Fig. 4, where the overlapping portions 920 are simply spot-welded as at 9y.

While it is possible to perform these operations by hand, my preferred method is to die-cut the circular disc with the slits; then die-stamp it to the form shown in Fig. 4;. then place it on a actlythe desired position, and then spot-weld the contacting overlapping portions as shown In said Fig. 4.

When made as above described, from stainless and mounting portions l3, M, which can be machined symmetrically with respect to the axis, with greatest accuracy, so that they can be relied upon to run in perfect centrifugal, or dynamic.

balance.

An important feature of the invention is, the

adjustable terminal nozzle 3|. In the position shown in Fig. 1, it can be adjusted so that the whirling, air-deflecting wind-wheel is far within the conduit, thereby projecting the flame as a concentrated small diameter column; or outside of the conduit, thereby producing a short bushy,

flame. of large diameter. As will be evident from Fig. 1, therange and adjustment of the nozzle 3| is such that its outlet edge 32 may be even farther,

in advance of the atomizer, than shown in said figure; or it may be adjusted rearwardly, the edge of the conduit at 33, being the limit of such rearward adjustment.

In practice, the size of the windwheel will be predetermined with reference to the cross-section and velocity of the air through the conduit 2 so as to be capable of properly atomizing and mixing with the air, the proper amount of oil required per unit volume of the air for efficient development of the fuel values of the oil, and production of the desired temperatures and amount of flame.

'The sleeve 3| will be adjusted, with respect to the windwheel, to suit the proportions anddimensions of the firebox and the desired distribution of the flametherein.

In operation, the oil is supplied through conduits 4, 5 and 1, preferably flowing by gravity under relatively slight pressure. When the fan I is not operating, the hub H of the windwheel will be firmly seated against the forward end of pipe 1 by the resilient operation of spring I9 through needle !5. When the fan is put in operation, the pressure of the air blast against the rear surfaces 9,

0a, of the windwheel will force the same forward, as indicated at l3, Fig. 1, thereby permitting escape of oil through the annular'outlet thus.un-

trifugally as a fine spray. This spray will be swept forward by the unimpeded high velocity part of the blast flowing in the annulus between the rim and the sleeve 3 I, so that in normal operation, the spray will not impinge upon the interior surface of the sleeve 3|.

Variations in the force of the air blast tend to vary the distance of outward movement of the windwheel and thereby tend to permit a greater or less flow of oil, according as the blast is greater or less. Preferably, however, the length of the sleeve portion 13 is great as compared with its normal range of axial movement; so that the decrease of flow resistance due to withdrawal-ch75 the hub 13 from tube 1, will be relatively small, large variations of oil supply being preferably taken care of by varying the pressure of the supply in pipe 4.

The mechanical interactions between the windwheel, air-blast, and liquid fuel are diverse and more or less complex.

Primarily, the windwheel is an air driven motor, rotation of which is caused by the air-blast driven at right angles to the plane of rotation, and impinging upon the inclined surfaces of the radiallydisposed blades. The air drives the blades in onedirection, clockwise in Fig. 4; and is itself deflected rearwardly or counterclockwise. For blades of any given pitch, the more slowly they move laterally, as compared with the speed of the airdraft, the more nearly will the rearward or counter-clockwise deflection of the air follow the pitch angles of the blades. Since the blades herein shown are not true-screw, air near the hub is deflected counter-clockwise more nearly to the plane of rotation, than the air impinging on surfaces more remote from the axis. Consequently, it is theoretically possible to have areas nearer the hub drive the extreme outer areas so fast that they begin to act as'fans, accelerating this part of the blast and deflecting it clockwise, that is, in the direction the windwheel rotates.

Outside of the blades, there is an annulus where the draft impinges at an acute angle on the outer cone surfaces 9a, and is outwardly deflected thereby. At very high speeds the friction of the surfaces Sa will have some tendency to drag this part of the air along with it in the direction of rota- .tion, that is, in a direction opposite to that of the inner annulus which is being deflected counterclockwise by the blades.

Outside of this cone surface So, there is another annular portion of the blast which has free passage between the periphery of the rotor and the sleeve 3|. This part of the blast is neither retarded, deflected rearwardly, nor dragged forwardly by the rotor; but it is compressed and forced to higher forward velocity by the annular part of the blast deflected from the steep cone surface 9a. This air in the outer annulus, being driven forward at high speeds, has its inner portion disturbed and cut up by the flaring or sawtooth periphery of the rotor. The high velocity of the outer annulus flowing past the periphery, has an injector action on the air which has reached the interior through the slots between the motor blades. The net result as concerns the air blast is a plurality of concentric regions of sharply different pressures, velocities and directions, resulting in vortex action of the air. This is well calculated to promote atomizing, evaporation and mixing of the liquid fuel with the air blast.

Considering now the liquid fuel, it is evident that the primary action of the rotor is that of a centrifugal projector, the projecting function being supplemented by very substantial atomizing function. Furthermore, it is particularly to be noted that the spray projected from the peripheral edges and tips is released in a region of particularly violent turbulence and vortex action.

Another aspect of this matter is that all work done on the liquid is a load on the motor; also that all turbulence produced in the air, at the periphery is a load on the motor; also that all friction, between the rotor and its mounting, is a load on the motor. An important factor of this load, is the viscosity of the oil in the thin annular space between the hub sleeve l3 and the tube l. "At high velocities, say 3,000 to 4,000 R. P. M..- these loads are quite substantial. these loads are, the less will be the speed at which the blades can be propelled circumferentially,

, relatively to the speed of the air-blast, and the greater will be the counter-clockwise or rearward deflection of the air impinging on the motor blades.

Incertain cases the load may be great enough relatively to the size of the windwheel and the velocity of the air-blast, so that the entire blade area will be required for motor purposes, and all of the air passing between the blades will be deflected, even at the periphery. In such case, the friction resistances which tend to increase as the square of the velocity, will operate to govem and determine a fairly definite constant speed for the rotor.

In case the proportions are such that the rotor. can accelerate to a high enough speed relatively to the volume and velocity of the air, the outer part of the motor blade area may move fast enough to lose all deflecting effect on the air, thereby becoming ineffective as motor area; and. if any higher speed is then reached, such outer blade area will begin to act as fan area, such area then becoming a dynamic load which must be carried by the parts of the blade area nearer the hub. By suitable designof the apparatus, this latter operation may be utilized to automatically govern the speed of the rotor; and thereby the centrifugal effect of the rotor in projecting the liquid fuel, may be predetermined and accurately governed within close limits.

It can be readily understood that when part of each blade near the hub, is'operating as a motor and deflecting the blast rearwardly, while part of the same blade out nearer the periphery is acting as a fan to propel the air forwardly; and an outer annulus beyond the periphery is tending to draw a vacuum inside the rim, an effective unique atomizing, vaporizing and mixing effect is produced.

In this connection, it is to be noted that the burner being of the gun type, the centrifugal rotor is relatively small, and is called upon to project very considerable volumes of oil, as compared with its diameter and surface area. This oil is delivered near the axis, that is, on or near the hub II, and a large part of it driven toward the periphery, along the rear surface of blades 9, under the influence of centrifugal force. As this oil travels toward the periphery, it is progressively accelerated from a relatively slowperipheral speed at the hub, to a relatively high peripheral speed at the rim. Consequently, its inertia causes it to lag toward the trailing edge, as, of each blade. See Figs. 3 and 4. At the same time, the air-blast is tending to drive oil in the same direction as said inertia lag, that is, toward said trailing edge, at, of the blade. Some of the oil reaching this edge may be driven off that edge under the influence of inertia and the airblast, but a substantial amount of it will follow said edge, outward to the rim, and such oil is delivered on the interior surface, 9:1: (Fig. 4) of the next succeeding blade.

One important feature of the invention is that the rim has a saw-tooth edge, the serrations of which, on the trailing edge, are nearly radial, and on the peripheral edge are long and sloping. This is for the purpose and with the result that most of the oil reaching the rim, is thrown from the sharp tipsof the serrations.

The greater This-'saw-tooth edge for the projector; is of greatladvantage in pr ojectin'g oil from a high speed rotor of an} oil burner, particularly, as comparedwitlr'a perfectly circular, thin or razor edge. Theftruez circle radial edge normally operates to centrifugallyzproject the oil in very fine droplets or mist,'but-under the conditions of practical use, exposed to very hightemperatures, it is found that any projecting carbon deposit such as sometimes. forms on a sharp circular edge, being of greateriradius thanfsuch edge, tends to throw a greatly disproportionate part of the oil and, in practice, aprojecting carbon formation of this kindlgrows and may ultimately operate to project substantially all of the oil; delivering it as a concentrated stream of la'rge droplets,instead of as an annular mist;

After much experimentation, I have discovered that in .my present construction, where the outward centrifugal progress of the fuel is along,

radial blades, the oil is proportioned equally between the sectors and will be projected from all of the tips, under all conditions of use. I.claim: V V

1. An oil burner including a blower and conduit for projecting a blast of air, a motor-sprayer substantially parallel with the air blast, said motor-sprayer embodying a' hub portion, rim

portion, andrintermediate propeller-like blades longitudinally inclined to deflect the blast away from the axis, and means for supplying liquid fuel upon the rear, blast-driven surfaces of said motor-sprayer.

3. An oil burner including a blower and conduit for projecting a blast of air, a rotary motor and sprayer of cup-like form rotatably mounted in said conduit and comprising a plurality of coacting members having convex outer surfaces presented rearwardly for impingement of the air blastthereon, and means forsupplying liquid fuelupon the rear, blast-driven surfaces of said motor-sprayer.

4. An oil burner including a blower and conduit'for projecting a blast of air, a rotary motor and sprayer ofcup-like form rotatably mounted in said conduit and comprising aplurality of coacting members having convex outer surfaces presented rearwardly for impingement of the air blast thereon and its central portion comprising fan-like blades, and means for supplying'liquid fuel upon the rear, blast-driven surfaces of said motor-sprayer. V

5. An oil'burner including a blower and conduit for projecting a blast of air, a rotary motor and sprayer of cup-like form rotatably mounted in said conduit and comprising a plurality of coacting members having convex outer surfaces presented rearwardly for impingement of the air blast thereon and its central portion comprising fan-like blades disposed as a relatively flat cone portion, and means for supplying liquid fuel upon the rear, blast-driven surfaces of said motorsprayer;

6. An oil burner including "a blower-and'conduit for projecting a blast of air, a rotary motor I and "sprayer-of cup-like form rotatably mounted in said conduit and comprising a plurality of coacting members having, convex outer surfaces presented rearwardlyfor impingement of the air blast thereon comprising fan-like blades dis-' posed as a central, relatively fiat cone portion and terminating in a peripheral conical rim portion of much steeper pitch, and means for supplying liquid fuel upon the rear, blast-driven surfaces of said motor-sprayer.

'7. An oil burner including a'blower and. conduit for projecting a blast of air, a rotary motor 8.'An oil burner includinga blower and con duit" for projecting a blast of air, a liquid fuel supply pipe mounted in said conduit, parallel withthe axis thereof and having its discharge outlet near the end of said conduit; and a motor sprayer windwheel having a hub of slightly smaller diameter than said supply pipe, slidably mounted in the outlet end'thereof, and having a surface adapted to fit and seal the fuel outlet; means urging said motor-sprayer rearwardly with force suflicient to close the outlet against the pressure of the oil supply, but insufiicient to prevent forward sliding of the windwheel and release of the oil when the air blast is in operation.

9. An oil burner including a blower and conduit for projecting a blast of air, a liquid fuel supply pipe mounted in said conduit, parallel with the axis; thereof and having its discharge outlet near the end of said conduit; a motor-sprayer windwheel rotatable and longitudinally slidable upon an axis substantially in alignment with the dischargeoutlet, and having a surface adapted to fit and seal the fuel outlet; means urging said motor-sprayer rearwardly with force sufficient to supply, butinsufiicient to prevent forward slidingof the windwheel and release of the oil when theair blast is in operation.

10. An .oil burner including means for supplying a draft of air and means for supplying a stream of .oil, in combination with a high speed centrifugal-projector for distributing the oil in the air d-raft,=the-oil delivering edge of said projector being thin and formed with inclined overlapped=- portions forming serrations, the trailing edges of said serrations being short and inclining but'slightly from" an axial radial plane passing therethrough, while'the leading edges are relatively'long andextend circularly at a relatively slight an'gle to theplane of rotation of said serrations- 11. Anioil burner including means forsupplying a draft of air 'andmeans for supplying a stream ofioil', in combination witha high speed centrifugal projector for distributing the oil in the air draft," the oil delivering edge of said projector I being thin and formed with serrations, eacli se'rratio'n having one relatively long edge of gradual "outwardslope in the direction of in-' the other edge being shorter and more nearly radial.

12. An oil burner including means for supplying a draft of air and means for supplying a stream of oil, in combination with a high speed centrifugal projector for distributing the oil in the air draft, said projector having a rim inclined outwardly in the direction of flow of the draft, the oil projecting edge of said rim being formed with serrations, each serration having one relatively long edge of gradual outward slope in the direction of inertia lag of the centrifugally projected oil, and the other edge being shorter and more nearly radial.

13. An oil burner including a blower and conduit for projecting a blast of air, a motor-sprayer windwheel in said conduit, near the discharge end thereof, said windwheel comprising a hub portion, rim portion, and intermediate outwardly and forwardly extending propeller-like blades connecting said hub and rim portions, and driven by and rotating about an axis substantially parallel with the air blast, and means for supplying coaxially with said windwheel, an annularly delivered, annularly spreading stream of liquid fuel upon the surfaces of said blast-driven propeller-like blades.

EDWARD O. BENJAMIN. 

